All the above agents are synthetic analogues, except Interferon which is a glycoprotein produced by many types of mammalian cells. It has been shown to be useful in treatment of hepatitis, papillomaviruses, hairy-cell leukemia and AIDS-related Kaposi's sarcoma. Idoxuridine, as its name implies, is a synthetic pyrimidine analog, which inhibits viral DNA polymerase. Zidovudine and zalcitabine are also synthetic pyrimidine analogs but they inhibit reverse transcriptase and act as chain terminators. Ref: Baden L.R., Dolin R. (2012). Chapter 178. Antiviral Chemotherapy, Excluding Antiretroviral Drugs. In D.L. Longo, A.S. Fauci, D.L. Kasper, S.L. Hauser, J.L. Jameson, J. Loscalzo (Eds), Harrison's Principles of Internal Medicine, 18e.